The  person  charging  this  material  is  re- 
sponsii>le  for  its  return  to  the  ^bra^y  f  °^^ 
Xch  it  was  withdrawn  on  or  before  the 
Latest  Date  stamped  below. 

Theft,  mutilation,  and  underlining  of  books 

are  reasons  for  disciplinary  action  and  may 

result  in  dismissal  from  the  University. 

«.    .>iiiur,i<:    ilRRARY    AT    URBANA-CHAMPAIGN 
UNIVERSITY    OF    IlLINOIS    LIBRAKT    ai 


FEB  1  2  19?5 

lEB  1 1  1975 
loEC  0  4  198' 


L161  — O-1096 


POISON  IVY 


BY 

JAMES  B.  McNAIR 
Associate  in  Economic  Botany 


Botany 
Leaflet  12 


FIELD  MUSEUM  OF  NATURAL  HISTORY 

CHICAGO 
1926 


LIST  OF  BOTANICAL  LEAFLETS  ISSUED  TO  DATE 

No.    1.  Figs $  .10 

No.    2.  The  Coco  Palm 10 

No.    3.  Wheat 10 

No.    4.  Cacao        10 

No.    5.  A  Fossil  Flower 10 

No.    6.  The  Cannon  Ball  Tree 10 

No.    7.  Spring  Wild  Flowers 25 

No.    8.  Spring  and  Early  Summer  Wild  Flowers      .     .        .25 

No.    9.  Summer  Wild  Flowers 25 

No.  10.  Autumn  Flowers  and  Fruits 25 

No.  11.  Common  Trees 25 

No.  12.  Poison  Ivy 25 

D.  C.  DAVIES,  Director 


FIELD  MUSEUM  OF  NATURAL  HISTORY 
CHICAGO,  U.S.A. 


LIBRARY 

OF  THE 

L'NIVEHSITV  Of  ILLINOIS 


LEAFLET  12. 


FRONTISPIECE. 


Photograph  by  R.  E.  Dahlyren. 

ON   RICH  SOIL  THE  POISON   IVY  CLIMBS  TREES  BY  MEANS  OF  ADVENTITIOUS  ROOTLETS. 


0. 


Field  Museum  of  Natural  History 

DEPARTMENT  OF  BOTANY 
Chicago,  1926 

Leaflet  Number  12 


Poison  Ivy 

Of  all  plant  pests  poison  ivy,  with  its  kindred 

species,  poison  oak  and  poison  sumac,  are  the  most 

dreaded.     It  is  well  known  that  the  slightest  contact 

with  the  sap,  the  broken  leaves  and  branches  gives  rise 

to  a  most  painful  irritation  and  itching  of  the  skin. 

.Some  persons  are  so  susceptible  that  they  are  seriously 

^affected  by  merely  handling  things  that  have  come 

r^into  contact  with  the  poison  ivy,  such  as  garden  tools 

r  or  the  clothing  of  one  who  has  walked  through  a  poison 

oivy  patch.     Few  fortunate  persons  are  naturally  im- 

*  mune. 

10         The  plants  that  cause  ivy  poisoning  are  botani- 

^cally  related,  in  fact  all  belong  to  one  genus,  Rhus, 

-^ which  includes  also  the  harmless  and  attractive  sumacs 

<^of  our  roadsides.    There  are  three  principal  poisonous 

'>  species  of  this  genus  in  the  eastern  United  States,  and 

one  on  the  Pacific  Coast.* 

^       The  first  and  most  common  of  the  eastern  species 

^^is  the  poison  ivy  itself,  known  botanically  as  Rhus 

,  Toxicodendron.     Its  species  name.  Toxicodendron,  is 

^composed  of  two  Greek  words  that  mean  "poison-tree." 

^Poison  ivy  is  easily  distinguished  by  its  compound 

r^leaves  of  three  leaflets.    Its  flowers,  which  appear  late 

in  spring,  are  clusters  of  inconspicuous,  greenish-white 

bloom,  followed  by  waxy  white  berries.     The  poison 

*See  J.  B.  McNair,  The  Taxonomy  of  Poison  Ivy.    Bot.  Ser. 
Field  Mus.  Nat.  Hist.  Vol.  IV,  No.  3,  1925. 

[169] 


2  Field  Museum  of  Natural  History 

ivy  has  two  principal  habits  of  growth,  being  either 
shrub  like  or  climbing.  In  one  habit,  the  plant  comes 
up  as  slender,  stiffly  erect,  little  branched  shrubs  from 
winding  underground  stems  or  rootstocks.  The  bark 
is  rather  smooth  and  light  gray.  The  height  is  usually 
from  one  to  three  feet,  though  in  rich,  moist  places  it 
may  reach  four  or  five.  In  the  other  growth-habit,  the 
main  stem  clambers  up  trees  and  over  rocks  or  walls, 
sending  out  aerial  roots  that  cling  like  those  of  the 
true  English  ivy.  Because  of  the  rooting  habit  of  this 
form  of  poison  ivy,  the  great  pioneer  botanist,  Linnaeus, 
who  never  saw  the  growing  plant,  considered  it  as  a 
separate  species  and  gave  it  a  separate  name,  Rhtis 
radicans — radicans  meaning  "rooting" — but  the  pres- 
ent-day tendency  is  to  regard  the  vine  simply  as  a 
climbing  form  of  a  more  or  less  variable  species.  In 
practically  all  the  states  of  the  Union  except  California, 
the  poison  ivy  is  found  as  a  shrub  where  the  woods  are 
open  and  rather  dry,  and  as  a  vine  where  they  are  rich 
and  moist.  Poison  ivy  vines  with  trunks  nearly  a  foot 
through  grow  in  the  "hammocks"  of  Florida. 

Very  closely  resembling  the  poison  ivy  are  two 
species  of  poison  oak,  Rhus  quercifolia  of  the  eastern 
states,  found  along  the  Atlantic  Coast  from  New  Jersey 
to  Texas,  and  Rhtis  diver siloba,  which  grows  in  Cali- 
fornia, Oregon,  and  Washington.  Both  of  these  plants 
look  so  much  like  the  poison  ivy  that  some  botanists 
have  tried  to  combine  the  three  species  into  one. 

The  most  vicious  member,  however,  of  this  whole 
undesirable  clan,  is  the  poison  sumac.  Fortunately, 
this  small  tree  is  usually  restricted  to  the  margins  of 
swamps,  which  are  seldom  visited  except  by  occasional 
hunters  and  naturalists.  Sometimes,  where  a  road  has 
been  built  through  a  bog,  a  clump  of  poison  sumac  will 
cause  a  great  deal  of  trouble.  Its  leaves  look  very  much 
like  those  of  the  common  wayside  sumac,  though  the 

[170] 


Poison  Ivy  3 

plants  are  actually  not  difficult  to  tell  apart.  In  the 
first  place,  the  common  sumac  never  grows  in  bogs, 
and  the  poisonous  variety  never  grows  anywhere  else. 
In  the  second,  the  fruits,  both  of  common  sumac  and 
of  the  staghorn  sumac,  another  ornamental  variety, 
are  red  and  grow  in  stiff,  erect  clusters  or  panicles, 
while  the  fruit  of  the  poison  sumac  is  a  drooping  bunch 
of  white  berries.  It  is  a  good  general  rule  that  white 
fruited  species  of  sumac  are  poisonous,  the  red  fruited 
ones  not. 

Sometimes  the  woodbine  or  Virginia  creeper,*  an 
ornamental  vine,  is  confused  with  poison  ivy  and  gets 
undeservedly  blamed.  The  confusion  is  easy  to  avoid. 
The  woodbine  always  has  five  leaflets  whereas  the 
poison  ivy  has  three,  hence  the  old  adage :  "Leaflets 
three,  let  it  be."  Moreover,  the  woodbine  does  not  sup- 
port itself  by  aerial  roots  like  the  poison  ivy  vine,  but 
climbs  like  a  grape  with  tendrils  terminating  in  disks. 
Finally,  its  fruit,  instead  of  being  an  elongated  cluster 
of  white  berries,  form  a  drooping,  flattened  bunch  of 
purple  berries. 

HOW  POISONING  TAKES  PLACE 

It  was  formerly  thought  that  the  pollen  of  poison 
ivy,  poison  oak,  and  poison  sumac  was  carried  by  the 
wind  and  caused  the  poisoning.  Their  pollen  is,  how- 
ever, sticky  and  is  never  carried  by  the  wind.  Further- 
more, it  is  not  poisonous.  It  may  in  fact  be  rubbed  on 
the  skin  of  people  easily  poisoned,  and  in  no  case  will 
poisoning  take  place.  Experimentation  has  shown 
that  neither  the  bark,  the  plant  hairs,  the  surface  of 
young  branches,  nor  the  surface  of  uninjured  leaves 
cause  poisoning  when  touched. 

*Psedera  quinque folia  (L.)  Green,  at  various  times  called 
Ampelopsis  and  Parthenocissus. 

[171] 


Field  Museum  of  Natural  History 


I 


CAttadenfium  Tlant,  Hiliorla.         97 
EDERA    TRIFOI^^i^^gANADENSIS. 


From  J.  P.  Cornut,  History  of  Canadian  Plants,  1635. 

THE  FIRST  PUBLISHED  ILLUSTRATION  OF  POISON  IVY. 


Poison  Ivy  5 

The  only  part  of  these  plants  that  will  cause  poi- 
soning is  the  sap.  If  a  stem  be  cut  in  half,  a  some- 
what milky  juice  will  be  seen  coming  out  in  small  drops 
from  the  outer  portions  of  the  stem.  This  outer  por- 
tion, the  bark,  and  soft  growing  layer  underneath,  cor- 
responds to  the  portion  of  the  willow  branch  and  elder- 
berry stem  used  for  whistles.  Under  a  microscope,  the 
resinous  sap  is  seen  to  come  from  small  tubelike  canals 
in  the  inner  layer  of  this,  the  bast.  Upon  thorough 
examination,  it  is  found  that  a  new  set  of  these  canals 
forms  with  each  spring  and  fall  growth  of  wood,  and 
that  each  separate  canal  is  surrounded  by  glandular 
cells.  These  small  cells  pour  their  poisonous  secretion 
into  the  canals.  The  canals  extend  from  the  smallest 
roots  to  the  smallest  branches  and  exist  even  within 
the  flowers,  fruits,  and  leaves.  In  the  stalk  of  the  leaf 
a  row  of  about  a  dozen  canals  is  found.  The  midrib 
and  large  veins  have  at  least  one  canal  each.  These 
poison  canals  are  found  to  extend  out  into  the  fine  net- 
work of  veins  in  the  leaf.  In  the  fruit,  which  has  some- 
what the  shape  of  a  mistletoe  berry,  many  poison  can- 
als surround  the  seed.  It  is  not  possible  to  break  any 
part  of  the  plants  without  rupturing  some  of  these 
canals  and  causing  the  poisonous  sap  to  come  out  on 
the  surface.  The  freed  sap  soon  darkens  and  hardens 
to  a  black,  shiny  varnish,  which  fully  protects  the 
wound.  An  oriental  relative  of  the  poison  sumac  thus 
gives  a  sap  which  forms  the  well-known  Chinese 
lacquer. 

The  young  leaves  of  the  plants  are  more  easily 
injured  than  the  mature  ones.  About  the  time  when 
people,  tired  of  being  shut  in  all  winter,  are  enjoying 
the  first  warm  days  of  spring  in  a  search  for  wild 
flowers,  the  plants  are  just  budding  out  and  not  easily 
noticed.  It  is  especially  at  this  time  of  the  year  that 
most  cases  of  ivy  poisoning  occur.     When  the  pollen 

[173] 


6  Field  Museum  of  Natural  History 

was  considered  dangerous,  ivy  poisoning  was  thought 
to  be  the  most  frequent  when  the  ivy  was  in  full  bloom, 
but  blossoming  does  not  take  place  until  the  leaves 
have  reached  their  full  growth,  that  is,  six  weeks  after 
the  plant  has  started  to  bud  out.  The  plants  are  poi- 
sonous all  the  year  around,  but  during  autumn  when 
the  leaves  become  red  and  bright  yellow,  they  are 
most  easily  noticed  and  avoided.  Cases  of  poisoning 
are  then  fewer  in  number  after  the  leaves  have  fallen, 
when  it  is  necessary  to  bruise  the  stems  to  get  in  touch 
with  the  poison. 

NATURE  OF  THE  POISON 

As  the  poison  canals  have  the  same  structure  as 
the  resin  canals  in  pine  trees  and  in  other  plants,  so 
one  might  expect  the  poison  to  be  of  a  resinous  nature. 
The  latest  work*  on  the  nature  of  the  poison  gives  the 
information  that  the  poison,  if  not  a  resin,  is  at  least 
intimately  mixed  with  a  resin.  It  is  a  clear  amber-red, 
sticky,  non-volatile  liquid  which  floats  on  water.  This 
sticky  substance  will  adhere  to  the  skin  like  pitch  and 
is  as  difficult  to  remove, 

SUSCEPTIBILITY  TO  THE  POISON 

It  has  been  found  that  only  about  one  person  in 
eighteen  is  badly  poisoned  by  ordinary  contact  with 
the  sap.  The  resistance  to  poisoning  appears  to  run 
in  families.  In  some  families  all  members  are  easily 
poisoned.  In  other  families  no  cases  of  poisoning  take 
place.  In  still  others,  one  parent  may  be  easily  poi- 
soned, while  the  children  may  not  be  susceptible,  or 
some  children  may  be  easily  poisoned.     Generally  if 

*  Those  interested  in  the  detailed  discussion  of  poison 
ivy,  its  poison  and  treatment  are  referred  to  the  book,  Rhus 
Dermatitis,  by  James  B.  McNair,  University  of  Chicago  Press, 
Chicago,  Illinois. 

[174] 


Poison  Ivy 


From  Host  and  Gilg. 


FLOWERS  AND  FRUIT  OF  POISON  IVY. 


8  Field  Museum  of  Natural  History 

both  parents  are  not  easily  poisoned,  the  children  are 
also  resistant.  However,  if  the  pure  poison  is  placed 
on  the  skin  of  a  person  considered  immune,  poisoning 
will  take  place.  Others  who  have  studied  the  subject 
find  that  a  person  may  be  easily  poisoned  one  year  and 
not  easily  poisoned  sometime  later.  The  reverse  is 
also  known  to  be  true.  Many  people,  wishing  to  gain 
resistance  to  the  poison  have  chewed  the  leaves  of  the 
plant,  or  swallowed  tea  made  from  the  leaves.  This 
has  been  followed  by  severe  cases  of  internal  poisoning. 
It  is  doubtful  if  immunity  to  the  poison  can  be  acquired 
in  this  manner,  as  the  poison  is  not  a  protein  and  no 
other  substances  are  known  to  produce  immunity.  A 
susceptible  person  may  certainly  be  severely  poisoned 
repeatedly  during  the  same  year.  Immunity  seems 
to  be  mostly  a  matter  of  thickness  and  condition  of  the 
skin.  Animals  are  generally  not  susceptible.  Goats 
will  thrive  on  it.  Cattle  and  horses  are  known  to  eat 
it  without  ill  effects. 

DESCRIPTION  OF  THE  DISEASE 

The  poison  may  penetrate  the  skin  by  means  of 
the  sweat  glands,  the  oil  glands,  the  hair  follicles,  or 
even  the  surface  of  the  skin  itself.  In  from  twelve 
hours  to  a  week  after  the  poison  has  been  placed  on 
the  skin,  a  reddening  and  itching  is  noticed.  The  poi- 
soning may  never  be  more  severe  than  this  or  it  may 
cause  blistering.  If  blisters  form  they  may  break  and 
allow  the  serum  to  run  freely  over  the  surface.  After 
about  a  week  this  condition  disappears  and  the  injured 
skin  falls  off  in  flakes.  The  poisoning  is  most  often 
experienced  between  the  fingers,  on  the  back  of  the 
hands,  on  the  forearms,  or  on  face.  It  is  very  seldom 
that  poisoning  takes  place  in  those  portions  of  the  body 
thickly  covered  by  hair,  although  it  may  affect  any 

[  176  J 


Poison  Ivy 


10  Field  Museum  of  Natural  History 

part  of  the  body  surface.  The  inside  of  the  hands  and 
soles  of  the  feet  are  seldom  poisoned  because  of  their 
thick  covering  of  skin.  The  ears  may  swell  up  to  a 
large  size  and  the  eyelids  may  become  so  swollen  as  to 
interfere  with  vision.  The  changes  in  the  skin  caused 
by  this  poison  are  not  easily  distinguished  from  con- 
ditions caused  by  other  skin  poisons  and  skin  diseases. 
If  a  person  has  been  in  a  locality  where  poison  ivy 
grows,  it  is  likely  that  poison  ivy  is  the  cause.  The 
distribution  of  the  blisters  on  the  skin  is  generally  in 
strips  or  patches  caused  by  contact  with  the  plant. 

REMEDIES  FOR  IVY  POISONING 

Numerous  methods  of  treatment  for  ivy  poisoning 
have  been  used  in  the  past.  There  is  no  real  cure  or 
preventative  that  will  take  the  place  of  caution.  The 
various  salts  of  lead  and  zinc  have  been  used  as  poison 
ivy  remedies.  They  neutralize  the  poison  to  a  certain 
extent,  but  not  completely.  The  best  and  most  effective 
preventative  proves  to  be  salts  of  iron,  particularly  iron 
chloride,  which  completely  neutralizes  the  poison, 
though  is  effective  as  a  remedy  only  if  used  in  the  very 
early  stages.  The  use  of  iron  chloride  to  the  extent  of 
five  percent  in  a  half  and  half  mixture  of  alcohol  and 
water  is  recommended.  If  the  hands  and  face  are 
bathed  freely  in  this  solution  either  before  or  imme- 
diately after  one  goes  into  a  region  known  to  contain 
poison  ivy  or  its  kindred  plants,  no  ill  effects  need  be 
expected.  The  remedy  is  cheap,  is  easily  obtainable  at 
any  drug  store,  is  non-poisonous  and  safe. 

In  ivy  poisoning  cases  that  actually  develop  and 
become  acute  the  treatment  is  based  on  a  recognition 
of  the  nature  of  the  injury.  The  effects  of  ivy  poison- 
ing on  the  skin  are  much  like  those  of  a  burn,  and  the 
treatment  suggested  resembles  that  successfully  used 
during  the  war  in  burn  cases.  The  affected  parts  are 
first  bathed  with  iron  chloride  solution,  to  neutralize 

[178] 


Poison  Ivy 


11 


SECTION  THROUGH  LEAF-RIB.      THE  POISONOUS  RESIN   IS  CONTAINED 
IN  THE   CENTRAL  DUCT. 


SECTION  THROUGH  STEM  SHOWING  THE  RESIN  DUCTS  (BLACK). 


12  Field  Museum  op  Natural  History 

the  poison.  Then  the  skin  is  dried,  and  melted  paraffin 
painted  over  it.  A  thin  sheet  of  cotton  is  laid  over  the 
wound,  and  this  also  is  covered  with  paraffin.  The  af- 
fected area  is  thus  protected  from  the  air  and  from 
rubbing,  and  new  skin  is  given  a  chance  to  form. 

ERADICATION  OF  THE  PLANT 

For  the  eradication  of  the  plants,  the  U.  S.  Dept. 
of  Agriculture  recommends  spraying  with  kerosene  or 
sodium  arsenite  solution  or  treating  the  cut  stems  with 
sulphuric  acid. 


In  the  Field  Museum  poison  ivy  plants  reproduced  in  fruit 
and  flower  and  models  of  the  enlarged  flowers  produced  in  the 
Stanley  Field  Plant  Reproduction  Laboratories  of  the  Museum,  are 
to  be  found  together  with  an  exhibit  of  other  plants  of  the  Sumac 
family  in  the  Hall  of  Plant  Life,  Hall  29  on  the  second  floor  east. 

The  poisonous  juice  of  the  related  lacquer  tree,  lacquered 
ware  and  economic  products  from  the  poison  ivy  relatives  are  with 
the  plant  economic  exhibits  in  the  adjoining  Hall  28. 


[180] 


